To further understand the effects of progesterone receptor modulators on the endometrium, we studied a woman with history of benign metastasizing leiomyoma who underwent medical treatment for 5 years with ulipristal acetate. Endometrial biopsies were performed at established intervals to monitor for intraepithelial neoplasia or progesterone receptor modulator-associated endometrial changes (PAECs). The patient tolerated UPA therapy well; there was no evidence of hyperplasia or proliferative changes associated with progesterone-associated endometrial changes. In this case prolonged exposure to ulipristal acetate did not result in premalignant or malignant endometrial pathology